Because of their high sintered density and inertness, sialon ceramic materials may potentially be used in many refractory and engineering applications. The term sialon is an acronym for a phase which contains the elements silicon, aluminum, oxygen and nitrogen. Sialon can also be described as a solid solution of alumina in silicon nitride. Appreciable amounts of solid solutioning produces a recognizable phase called .beta.' sialon. This phase can hold up to 60% alumina in solid solution. Amounts greater than 60% are exsolved and occur as free alumina. Numerous other sialon phases arise in the sialon system depending on the relative proportions of the starting materials and the amounts of AlN or oxygen present during formation of sialon.
Most prior art techniques relating to methods of preparing sialon involve the use of expensive starting materials, such as silicon nitride, and/or aluminum nitride. Only a few researchers have studied lower cost means of producing high purity sialon. U.S. Pat. No. 4,243,621 to Mori et al teaches a method of preparing sialon by premixing two metals (Si+Al) and an oxide, forming a shape, and firing this shape in a nitrogenous atmosphere. U.S. Pat. No. 4,184,884 to Jong, teaches a method of making sialon by using silicon, alumina and aluminum or aluminum nitride.
Disadvantages of the prior art techniques include the use of high cost starting materials, the use of aluminum metal which has severe limitations due to its explosive tendency, and the use of aluminum nitride due to its high cost and tendency to react with moisture. Attempts to produce commercial quantities of sialon based on prior art techniques would be prohibitively expensive. Therefore, it is an object of this invention to provide a method of preparing high purity sialon at relatively low cost.